Silibinin regulates gene expression, production and secretion of mucin from cultured airway epithelial cells.

We investigated whether silibinin significantly affects gene expression, production and secretion of mucin from cultured airway epithelial cells. Confluent NCI-H292 cells were pretreated with silibinin for 30 min and then stimulated with epidermal growth factor (EGF), phorbol 12-myristate 13-acetate (PMA) or TNF-α for 24 h. The MUC5AC mucin gene expression and mucin protein production were measured by reverse transcription-polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay (ELISA). The effect of silibinin on TNF-α-induced activation of NF-κB p65 was also examined. Confluent primary rat tracheal surface epithelial (RTSE) cells were pretreated with adenosine triphosphate (ATP) for 5 min and then treated for 30 min in the presence of silibinin to assess the effect on mucin secretion using ELISA. The results were as follows: (i) silibinin inhibited the expression of the MUC5AC mucin gene induced by EGF, PMA or TNF-α from NCI-H292 cells; (ii) silibinin also inhibited the production of MUC5AC mucin protein induced by the same inducers from NCI-H292 cells; (iii) silibinin inhibited the activation of NF-κB p65 by TNF-α in NCI-H292 cells; (iv) silibinin significantly decreased ATP-induced mucin secretion from cultured RTSE cells. This result suggests that silibinin can regulate gene expression, production and secretion of mucin by directly acting on airway epithelial cells.